A diesel-electric locomotive typically includes a diesel internal combustion engine coupled to drive a rotor of at least one traction alternator to produce alternating current (AC) electrical power. The traction alternator may be electrically coupled to power one or more electric traction motors mechanically coupled to apply torque to one or more axles of the locomotive. The traction motors may include AC motors operable with AC power, or direct current motors operable with direct current (DC) power. For DC motor operation, a rectifier may be provided to convert the AC power produced by the traction alternator to DC power for powering the DC motors.
AC-motor-equipped locomotives typically exhibit better performance and have higher reliability and lower maintenance than DC-motor-equipped locomotives. In addition, more responsive individual motor control may be provided in AC-motor-equipped locomotives, for example, via use of inverter-based motor control. However, DC-motor-equipped locomotives are relatively less expensive than comparable AC-motor-equipped locomotives. Thus, for certain hauling applications, such as when hauling relatively light freight and/or relatively short trains, it may be more cost efficient to use a DC-motor-equipped locomotive instead of an AC-motor-equipped locomotive.
For relatively heavy hauling applications, diesel-electric locomotives are typically configured to have two trucks including three powered axles per truck. Each axle of the truck is typically coupled, via a gear set, to a respective motor mounted in the truck near the axle. Each axle is mounted to the truck via a suspension assembly that typically includes one or more springs for transferring a respective portion of a locomotive weight (including a locomotive body weight and a locomotive truck weight) to the axle while allowing some degree of movement of the axle relative to the truck.
A locomotive body weight is typically configured to be about equally distributed between the two trucks. The locomotive weight is usually further configured to be symmetrically distributed among the axles of the trucks. For example, a conventional locomotive weighing 420,000 pounds is typically configured to equally distribute weight to the six axles of the locomotive, so that each axle supports a force of 420,000/6 pounds per axle, or 70,000 pounds per axle.
Locomotives are typically manufactured to distribute weight symmetrically to the trucks and then to the axles of the trucks so that relatively equal portions of the weight of the locomotive are distributed to the axles. Typically, the weight of the locomotive and the power rating of the locomotive determine a tractive effort capability rating of the locomotive that may be expressed as weight times a tractive effort rating. Accordingly, the weight applied to each of the axles times the tractive effort that can be applied to the axle determines a power capability of the corresponding axle. Consequently, the heavier a locomotive, the more tractive effort that it can generate at a certain speed. Additional weight, or ballast, may be added to a locomotive to bring it up to a desired overall weight for achieving a desired tractive effort capability rating. For example, due to manufacturing tolerances that may result in varying overall weights among locomotives built to a same specification, locomotives are commonly configured to be slightly lighter than required to meet a desired tractive effort rating, and then ballast is added to reach a desired overall weight capable of meeting the desired tractive effort rating.
Diesel engine powered locomotives represent a major capital expenditure for railroads, including both the initial purchase of a locomotive, but also the ongoing expense of maintaining and repairing the locomotive. In addition, hauling requirements may change over time for the railroad, so that a locomotive having a certain operating capability at a time of purchase may not meet the hauling needs of the railroad in the future. For example, a railroad looking to purchase a locomotive may only have minimal hauling needs that may be met by a relatively inexpensive low tractive effort capability locomotive, such as a DC powered locomotive having less hauling capability compared to a more expensive relatively high tractive effort locomotive, such as an AC powered locomotive. However, at some point in the useful life of the low tractive effort capability locomotive, hauling needs of the railroad may change, such that the low tractive effort capability locomotive may not be able to provide sufficient hauling capability. As a result, the railroad may need to purchase a more capable high tractive effort capability locomotive, thereby sacrificing a remaining useful life of the low tractive effort capability locomotive.
The inventors have recognized that by manufacturing one type of an item, instead of various different types of the item, a manufacturer may be able to reduce manufacturing costs by streamlining production lines. For example, a locomotive manufacturer may be able to reduce manufacturing costs by producing a single type of locomotive, such as a high tractive effort capability AC powered locomotive, instead of producing two types of locomotives, such as a high tractive effort capability AC powered locomotive and a low tractive effort capability DC powered locomotive. Thus, what is needed is a locomotive that, for example, may be easily reconfigured as operating requirements for the locomotive change over its life. There is also a continuing need to reduce manufacturing and equipment costs. Accordingly, the inventors have innovatively developed a reconfigurable locomotive that may be ballasted using less weight than typically required and may allow for elimination of a need for costly ballast altogether.